I know, I know. It’s an impossible choice. I’d be so torn between several: camera, notes, music, messages, tasks…
And, as nerdy as it sounds, I think I’d pick the app Things. (The to-do list manager.)
It feels like cheating to choose a web browser, as Shawn notes, so I think I’d go with Pocket Casts. I spend too much time listening to podcasts while I’m mowing the lawn, doing dishes, driving, and more.